1. Field of the Invention
The present invention relates in general to multi-meters, and more particularly to a multi-meter which is capable of measuring a Z-state of an output signal from a thing to be measured, in addition to high and low states thereof, the Z-state being an unknown state unrelated to the high and low states.
2. Description of the Prior Art
Multi-meters are generally classified into two types, a digital type and an analog type.
Referring to FIG. 1, there is shown a perspective view illustrating schematically a construction of a conventional multi-meter of the analog type. In this drawing, the conventional multi-meter of the analog type is designated by the reference numeral 1. As shown in this drawing, the conventional multi-meter 1 of the analog type comprises a body 2, a switch 3 disposed on a lower front portion of the body 2 to select an object and a range to be measured, probes 4 connected to the body 2 through cables 5, and an indicator 6 disposed on an upper front portion of the body 2 to indicate a scale on a scale board corresponding to a measured value.
Also, objects to be measured such as, for example, direct current (DC) current and voltage, an alternating current (AC) voltage, a resistance (.OMEGA.) and etc. and ranges thereof to be measured are indicated on the front of the body 2 surrounding the switch 3.
FIG. 2 is a perspective view illustrating schematically a construction of a conventional multi-meter of the digital type, which is designated by the reference numeral 11 in the drawing. As shown in this drawing, the conventional multi-meter 11 of the digital type comprises a body 12, a switch 13 disposed on a lower front portion of the body 12 to select an object and a range to be measured, probes 14 connected to the body 12 through cables 15, and a display unit 16 disposed on an upper front portion of the body 12 to display a numerical value corresponding to a measured value.
The objects to be measured such as the DC current and voltage, the AC voltage, the resistance (.OMEGA.) and etc. and the ranges thereof to be measured are also indicated on the front of the body 12 surrounding the switch 13.
The operations of the multi-meters of the analog and digital types with the above-mentioned constructions will hereinafter be described with reference to FIGS. 1 and 2.
First, in the case where the user operates the switch 3 of the multi-meter 1 of the analog type to select an object and a range to be measured and then brings the probes 4 into contact with a desired position of a thing to be measured, a hand of the indicator 6 indicates a scale on the scale board corresponding to a measured value. Then, the user recognizes the measured value by reading the scale indicated by the hand of the indicator 6.
On the other hand, in the case where the user operates the switch 13 of the multi-meter 11 of the digital type to select an object and a range to be measured and then brings the probes 14 into contact with a desired position of a thing to be measured, the display unit 16 displays a numerical value corresponding to a measured value. Then, the user recognizes the measured value directly from the numerical value displayed on the display unit 16.
By the way, the above-mentioned conventional multi-meter of the digital type is generally constructed to measure only two level states, high and low states of an output signal from the thing to be measured, such as, for example, an integrated circuit. For this reason, in the case where the integrated circuit outputs a signal of a Z-state as well as the high and low states, the above-mentioned conventional multi-meter of the digital type cannot measure the Z-state. As a result, an output characteristic of the integrated circuit cannot be accurately grasped.